Probabilistic assessment of the impact of bottom sediment on doses to humans from a groundwater-mediated radionuclide release in a farm-lake scenario

Abstract

Radionuclide transport with groundwater flow and subsequent doses to<br/>people are an aspect to be studied when assessing the long-term safety of<br/>geological nuclear waste repositories. A scenario where the radionuclide<br/>release migrates through a three-layer sediment structure of a lake in a<br/>farming environment is presented in this paper. The sediment column con-<br/>sists of deep (till), intermediate (glacio-aquatic sediment) and top layers<br/>(clay). The radionuclide release is assumed to enter the deep sediment layer<br/>from a bedrock fracture system at a rate of 1 Bq yr−1. The main objectives of<br/>the paper are to investigate the most contributing parameters, especially<br/>linked to the sediment layers, to the overall dose estimates for humans. The<br/>sensitivity analysis was conducted in two phases where the Morris method<br/>was used for screening and the Extended Fourier Amplitude Sensitivity<br/>Testing and Sobol’s methods were used for estimating total-order indices.<br/>The studied radionuclides, 36Cl, 135Cs, 129I, 94Nb, 237Np, 90Sr, 99Tc and 238U,<br/>exhibit differences in how the sediment layers affect the concentration in the<br/>lake water used for drinking, irrigation and watering cattle and subsequently<br/>the dose conversion factors for humans through ingestion, inhalation and<br/>external radiation.